Dry chemical fire extinguisher
composition



United States Patent 3,172,852 DRY CHEMICAL FERE EXTINGUISHER COMPOSITION Zbigniew J. Lobos, Monmouth liunction, N.J., assignor to Stop-Fire, Inc., New Brunswick, NJ. No Drawing. Filed Jan. 31, 1961, Ser. No. 85,966 1 Claim. (Cl. 252) This invention relates to fire extinguishing compositions and more particularly to a relatively dry, free-flowing chemical powder which is useful in combatting all types of fires including metal fires.

Conventional fire extinguishing powders, such as sodium bicarbonate or the like carbonate base compositions are suitable for use in fighting burning oils, greases, and flammable liquids, and which are known as class B fires. The carbonate base dry powders are also useful for combatting electrical equipment fires which are known as class C fires. The dry carbonate base powders, however, are relatively ineffective for use in combatting ordinary wood and coal fires, and such as classified as class A fires. This is because the carbonate material does not stick to the hot surfaces of the burning material. As a consequence, re-ignition and back fires result. For the same reason such dry powders are ineffective for extinguishing metal fires because of the violent and explosive reaction created between the burning metal and their decomposition products. There is accordingly an urgent need for a dry, chemical powder which is useful in combatting all classes of fires as well as metal fires. The present invention provides such a composition.

Attempts have been made heretofore to provide improved fire extinguishing compositions, and various chemicals have been employed. Use has been made of boric acid and ammonium salts of sulfuric as well as phosphoric acid. These substances melt at relatively high temperatures, such as produced on burning wood, coal and metals, and form a thin layer or coating of the melted salts on the burning surfaces. Also solutions of these salts have been used to saturate wood, textiles and the like to render them fire resistant. Use of these high temperature melting substances in dry powder fire extinguishing compositions have been ineffective because the protective coating formed is too thin and fails to prevent the occurrence of back fires and re-flaming of the fire after being apparently put out.

Some improvement has been obtained with the use of compositions comprising a finely divided mixture of a phosphate, e.g., monoammonium phosphate and an aldehyde type resin such as urea formaldehyde or the like synthetic resin, and including organic material such as dried waste sulfite liquor and inorganic substances, e.g., silica, etc. The phosphate acid salt may be replaced by boric acid or boric acid salts to provide a foam-forming mate- 'rial. The disadvantages encountered with the use of these compositions has been that it is necessary to incorporate a relatively large amount to 30% by Weight of the composition) of organic material, and which is combustible thus lowering the efficiency of the composition in combatting fires, especially class B fires.

In accordance with the present invention, it has been discovered, unexpectedly, that these disadvantages may be overcome by employing a dry mixture in which the essen tial constituents present or produced during treatment of the fire are monoammonium-metal-phosphate and carbon dioxide gas. The chemical reaction is represented by the following equation, where M is a metal NH H PO +MCO NH MPO +CO +H O In the above reaction carbon dioxide saturates. the melted mixture in the form of bubbles to produce a foamy ice mass. The mass is of very low density, and after the reaction takes place, the resulting product is a white, solid, spongy mass of very low bulk density resembling a plastic sponge in appearance. The spongy porous mass sticks firmly to the hot surfaces of the burning material, such as wood, coal, metal, etc., and cuts off the access of air, thus extinguishing the fire. The spongy mass is four or more times greater in volume than the volume of an equal weight of pure melted monoammonium phosphate.

The metal carbonates used are those which are in the form of a dry powder, and such as react with monoammonium phosphate when applied to the hot burning mass with evolution of CO gas. Carbonates which react with the phosphate at room temperature F.) are thereabouts or in the presence of moisture, e.g., in an atmosphere of relative humidity are not suitable. Further, the carbonates of sodium, potassium and ammonium are not suitable because they are highly reactive with ammonium phosphate, especially in the presence of moisture. Calcium carbonate, although much less reactive, is also not used for the same reason. Carbonates which are poisonous, such as barium, lead and the like, are not suitable. The carbonates of cobalt, chromium, cadmium and bismuth may be used but they are relatively expensive. It is desired to provide a commercially inexpensive dry chemical fire extinguishing composition in accordance with the present invention.

Metal carbonates which have been found to be the most useful are those of magnesium. Native magnesite in the form of finely ground particles of approximately 200 mesh has been found to be very satisfactory. Magnesite (MgCO reacts readily with monoammonium phosphate when they are heated together, as upon application of the composition to a conflagration. They do not, however, react appreciably at ordinary room temperature or in the cold, even in the presence of moisture and which is a desirable property. Magnesite is relatively inexpensive, is non-poisonous, and abundant commercially. It has a high bulking density which is a very desirable physical characteristic property. Magnesite may be used alone or mixed with hydrated or heavy magnesium carbonate (MgCO .5H O) such as used in paints, insecticides and the like. The heavy magnesium carbonate may be present in small amounts up to one-third of the magnesite present in the dry composition. Similarly tricalcium phosphate may be substituted for the heavy magnesium carbonate and in like small amounts, e.g., 5 to 10% of the monoammonium phosphate present in the dry composition, the principal and essential constituents being the ammonium phosphate and magnesium carbonate. Preferably the dry fire extinguishing powder composition contains between 10 and 35% by weight of magnesium carbonate.

The dry particles of the composition are coated with silicone resin to make them free flowing and resistant to caking. As the activator in the process of polymerization of silicons magnesium carbonate (heavy) is preferred, other carbonates e.g., zinc, nickel carbonate and/or precipitated phosphate may be used either alone or as mixtures of one or more of these substances.

It is a principal object of the present invention to provide a dry chemical fire extinguishing composition which is adapted for application to all classes of fires. The composition is free of cellulose and organic substances, the presence of which lowers the efficiency of the composition as a fire extinguisher.

Another object of the invention is to provide a fire extinguishing composition in the form of a dry powder which has the following properties (1) It is adapted to extinguish all classes of fires including metal fires.

(2) It contains only inorganic nonhygroscopic fire extinguishing constituents.

(3) It is resistant to moisture and can withsstand an atmosphere of 90% relative humidity without deterioration.

(4) It is foam compatible and forms a spongy mass which clings tenaceously to the hot surface of the burning material thus smothering out the fire.

These and other objects and advantages of the invention will become apparent to those skilled in the art from the following description.

Typical mixtures which produce free flowing fire extinguishing composition are given in the following examples, the parts being by weight- Example 1 Parts by weight Monoammonium phosphate 79.0 Magnesium carbonate (magnesite), 200 mesh 15.0 Tricalcium phosphate (precipitated) 5.0 Silica (300 mesh particles) 0.4 Silicone (dimethyldiethoxysilane) 0.6

" Example 2 Monoammonium phosphate 79.0 Magnesium carbonate (magnesite) 200 mesh 15.0 Magnesum carbonate (heavy MgCO .5l-I O) 5.0 Silica (300 mesh particles) 0.4- Silicone (Ex. 1) 0.6

Example 3 Monoamrnonium phosphate 69.0 Magnesium carbonate (Ex. 1) 25.0 Magnesium carbonate (heavy, Ex. 2) 5.0 Silica (Ex. 1) 0.4 Silicone 1 0.6

1 5050 mixture of dimethyldiethoxysilane and allyltrichlorosilune.

Example 4 Monoammonium phosphate 64.0 Magnesium carbonate (Ex. 1) 30.4 Nickel carbonate (200 mesh) 5.0 Silicone (diphenyldihydroxysilane) 0.6

Example 5 Monoammonium phosphate 83.4 Magnesium carbonate (Ex. 1) 10.0 Tricalcium phosphate (Ex. 1) 3.0 Nickel carbonate (200 mesh) 3.0 Silicone (dimethyldichlorosilane) 0.6 v

The ingredients of the compositions as set out in the foregoing examples are initially admixed, except for the silicone, for example using a conventional ribbon mixer for approximately 30 minutes. During the last to minutes of mixing, the silicone is added slowly and the whole mass continued mixing for another to 45 minutes or longer, to produce a homogeneous mixture wherein each of the particles are coated with silicone resin. The mixture is then poured into drums or a suitable container as stored at room temperature (70 F.) for approximately twelve hours or overnight to permit polymerization of the silicone. The next day the dry, powder mixture is poured into the fire extinguishing container for distribution and use. The addition of the super-fine silica substantially enhances the free flowing properties of the dry mixture. The fire extinguishing composition of the invention is completely foam compatible, being free of fatty acid salts, and which permits the composition to be used together with mechanical foam such as may be discharged from other type fire extinguishers, and without danger of destroying such foams. The fire extinguishing composition of the invention thus complies with the regulations promulgated by the United States Coast Guard.

While magnesium carbonate works best when added to the mixture in amounts between about 10 and by Weight of the total dry composition, it has been found that proportionate amounts as low as 2 to 5% of magnesium carbonate enhances the efficiency of the composition by increasing the volume of the melted mass when used to fight fires. It has also been found that for use in combatting wood fires the presence of as much as by weight magnesium carbonate provides an excellent dry powder composition. In fighting magnesium metal fires, however, the proportionate amount of magnesium carbonate should be held within the range of 10 to 35% as aforementioned. An overall range content of magnesium carbonate is from 2% to 70% of the fire extinguishing composition.

The preferred amount of monoamrnonium phosphate present has been found to range from 59% to 84% by weight based on the dry mixture. As a broad minimum and maximum range the content of monoammonium phosphate should be between 24% and 92% by weight of the composition.

The finished product, after polymerization of the silicone coating, has excellent free-flowing properties, is water repellent and highly resistant to caking. The dry, granular product can be passed through valve controlled nozzles without clogging and applied to fires as fiuid stream-like mass of particles. A heavy blanket of the free-flowing powder composition eifectively smothers and cools fires, quickly extinguishes them. Such silicone coated powders of the invention have been found to possess enhanced fire extinguishing properties over ordinary particles uncoated with silicone polymerizates.

The silicones useful in producing the free-flowing fire extinguishing powder, and which may be polymerized without heat and solvents are the silanes and the polysiloxanes which undergo further polymerization. Suitable silicones employed to coat the finely divided particles are preferably ones which may be polymerized to form a cross linked polysiloxane. It is desirable to use a trifunctional silicone which is capable of becoming cross-linked upon polymerization on the finely divided solid particles whereby the particles are rendered water repellent.

Among the polysiloxanes useful are the alkyl trihalosilanes, e.g., methyltrichlorosilane, amyltrichlorosilanes, octadecyltrichlorosilane, cyclohexyltrichlorosilane, allyltrichlorosilane, vinyltrichlorosilane, and aryltrihalosilanes including phenyltrichlorosilane and alkylalkoxysilanes, e.g., methyltriethoxysilane etc, and mixtures or blends thereof. Also copolymerized polysiloxanes by hydrolysis with difunctional silanes, such as dimethyldiethoxysilane, dimethyldichlorosilane and diphenyldihydrosilane.

The silicones are available commercially, and marketed by Dow Corning as DC1107 and -1108. The General Electric Company also supplies a silicone liquid Dri- Film 268 silicone fluid which is a blend of partially hydrolyzed methylhydrogen polysiloxanes. A silicone useful consists of a 50-50 mixture, by volume, of dimethyldiethoxysilane and phenyltrichlorosilane.

During use of the fire extinguishing composition a chemical reaction takes place between the monoammonium phosphate and magnesium carbonate to release carbon dioxide, Water and form the corresponding ammonium-metal-phosphate, the latter with some excess of unreacted monoammoniurn phosphate melting on the hot burning surfaces, and producing an adherent foamy mass which smothers out the fire. The fire extinguishing action of the combination of the phosphate and magnesium carbonate is substantially greater than either one alone and thus a synergistic action results which makes the composition an efficient fire extinguisher for combatting all types or classes of fires.

While the invention has been described with particular reference to specific compositions, such as typified by the examples, it will be understood that other embodiments thereof may be made without departing from the spirit and scope of the invention and as defined in the appended claim.

5 What is claimed is: A dry free flowing chemical powder for application to fires to extinguish the same, said free flowing chemical powder consisting essentially of the following constituents 623,657 in parts by weight- 5 1,428,207 monoamrnonium phosphate 79.0 230L428 magnesite, 200 mesh 15.0

tricalcium phosphate, precipitated 5.0

silica, 300 mesh 0.4 815,712 dimethyldiethoxysilane 0.6 10

References Cited in the file of this patent UNITED STATES PATENTS Edwards Apr. 25, 1899 I Biddle Sept. 5, 1922 Schulenburg Aug. 25, 1959 FOREIGN PATENTS Great Britain July 1, 1959 

